This invention relates to shaft couplings, and more particularly to improvements in couplings of the type that use a grid of metal rungs to join coupling halves.
A common form of flexible coupling used for joining driving and driven shafts utilizes a metal grid to join coupling halves mounted on the shafts being coupled. The grid is often formed as a serpentine with straight grid rungs joined together at alternate ends by integral end loops. The rungs are received in radially aligned, axially extending slots formed between metal teeth on each of the coupling hubs. The rungs span the space between the coupling halves and act to transmit torque between the hubs. The side walls of the teeth are generally curved in an axial direction so that the unsupported length of each rung is reduced as the torsional load transmitted between the coupling halves increases. An early example of this type of flexible coupling is found in U.S. Pat. No. 1,763,842 issued June 17, 1930 to Bibby.
In the prior flexible couplings of this type, the rungs and the hubs are made of metal, usually steel, and the rungs are heat treated.
This form of flexible coupling provides an effective device for joining shafts. However, because of variations in the circumferential tooth spacing and grid rung spacing and parallelism resulting from the manufacturing processes, under a given load one or more rungs may be out of full contact with the adjacent teeth. This is particularly true at lower torque loads. Such uneven contact means that all grid rungs and all teeth will not carry the same load and an undesirable uneven load distribution is the result. Thus far, the inherent flexibility of the grid has been relied upon to eventually, at high load, evenly distribute the load between all rungs and all teeth.